Abstract 16139: Differences in Endo and Epicardial Substrate of Post-Infarction Ventricular Tachycardias Identified by Magnetic Resonance-Based Signal Intensity Mapping
Background: a substantial number of post-infarction ventricular tachycardias (VT) are located in the epicardium. The characterization of substrate differences between endo and epicardial VT would define the optimal ablation strategy.
Hypothesis: differences in endo-epicardial VT substrate may be identified by magnetic resonance-based signal intensity (SI) mapping.
Methods: in a swine model of post-infarction VT (31 animals), a contrast-enhanced magnetic resonance imaging (ceMRI) was performed 4-16 week after the infarction, followed by an electrophysiological study with endo-epicardial electroanatomic mapping for scar analysis and VT induction. SI maps were obtained from ceMRI, using a customized software, and were color coded as follows: red for dense scar defined by a SI 3 SD higher than remote normal myocardium (magenta) and heterogeneous tissue (HT) in between these extremes. Conduction velocity was also estimated in endocardium and epicardium in 10 animals.
Results: 13 epicardial VT and 17 endocardial VT were induced. Cycle length was significantly longer in epicardial VT (329±49 vs 267±31 ms, p=0.003). Scars of animals with inducible epicardial VT were characterized by a patchy pattern, with more than 2 HT channels (100% vs 35%, p=0.003) (figure, panels A and B), less dense scar (5±2 vs 10±6 cm2, p=0.01) and a larger proportion of HT/scar (76% vs 61%, p=0.003) compared to those without inducible epicardial VT. Endocardial VT related scars frequently showed a single HT channel (82% vs 36%, p=0.02) (figure, panels C y D); whereas dense scar areas (11±4 vs 8±5 cm2, p=NS) and HT/scar proportion (62% vs 67%, p=NS) were similar. In addition, the estimated conduction velocity was lower in the epicardium than the endocardium (0.28±0.05 vs. 0.54±0.21 m/s, p=0.02).
Conclusions: Epicardial VT substrate seems to involve patchy scars with several HT channels per scar; whereas endocardial VT substrate is characterized by larger dense scars involving single HT channels.
- © 2013 by American Heart Association, Inc.